This invention relates to a centrifuge in which a rotor carrying a sample is driven at high speed for separation, sedimentation, concentration or the like of the sample and, more particularly, to a cooling structure adapted for suppressing a temperature rise of the centrifuge.
In a centrifuge, a rotor carrying a sample is driven at high speed, so the rotor generally generates heat due to its friction with air, and the sample is likely to be degenerated or destroyed by the heat. To avoid this, the rotor is cooled.
The simplest cooling method that has been employed in the prior art is to utilize a cooling structure in which air is blown off by the rotation of a rotor in a rotor housing and exhausted therefrom through its outlet ports to lower the atmospheric pressure in the rotor housing and, at the same time, air is drawn in from the outside through an inlet port formed in a cover of the rotor housing adjacent the position of the lowest atmospheric pressure in the rotor housing, that is, the center of rotation of the rotor, the air thus drawn into the rotor housing being similarly blown off by the revolving rotor to be forced out of the rotor housing. By such ventilation of the rotor housing, a temperature rise of the rotor is suppressed to keep the rotor at room temperature under which the centrifuge is placed.
This cooling structure achieves cooling of the rotor housing by automatically drawing air from the exterior and expelling it outside without involving a forced air supply, and hence is very convenient. But, as a motor for driving the rotor is driven at an appreciably high speed, heat is also generated from the rotor itself to heat the rotor, resulting in the likelihood of causing a temperature rise of the sample.
In view of this, it has been proposed to incorporate a fan in the motor and drive it with the rotation of the motor to draw in air to cool the motor. In this case, the additional provision of the fan inevitably makes the motor structure bulky, and since the resistance to the air supply by the fan is large, the motor itself must be designed to compensate for the resulting energy loss. Further, this method presents a problem of noise generation by the fan.
It is also possible to enlarge the outlet ports for passing air into and out of the rotor housing in large quantity to provide for enhanced cooling effect. In this instance, however, the air resistance of the rotor to the air stream markedly increases, which leads to the defect that the power of the motor used must be large correspondingly.
An object of this invention is to provide a cooling structure of simple construction for centrifuges which is designed not only to cool a rotor with gas but also to cool a motor with the gas employed for cooling the rotor.
Another object of this invention is to provide a cooling structure for centrifuges which is adapted so that air is automatically drawn into a rotor housing and then discharged therefrom to flow into a motor to cool it.
Still another object of this invention is to provide a cooling structure for centrifuges which enables cooling of a motor without attaching thereto a fan and which is of small size as a whole but of low noise.